The present invention relates to organometallic halides obtained in a novel form and to a process for their preparation. More precisely the invention relates to the synthesis of organic halides of magnesium (the so-called Grignard reagents), zinc (the so-called Blaise reagents), beryllium, and calcium. The invention also relates to the use of Grignard reagents prepared according to this process for the synthesis of anhydrous magnesium halides.
The production of organomagnesium halides by the reaction between magnesium and a hydrocarbon halide in the presence of a solvent such as an ether or a hydrocarbon has long been known. More recently, German Pat. No. 847,595 has described their synthesis without solvent by the reaction between magnesium powder and a liquid hydrocarbon halide. A similar method has been described by Tetrahedron Letters 14, 633 (1962). Likewise, Y. GAULT has published in Tetrahedron Letters 1, 69 (1966) a synthesis without solvent at 0.degree. C. by adsorption at 20 to 200 mm Hg on films of magnesium evaporated under high vacuum. This process requires costly operating conditions and cannot easily be extrapolated to an industrial scale.
A characteristic common to all the aforesaid methods is the use of at least one liquid compound, which results in either the necessity of using the Grignard reagent in the presence of the liquid compound or the necessity of providing a costly supplementary treatment for isolating the Grignard reagent.
Moreover, the formula of Grignard reagents prepared in a solvent has been discussed at length by scientists, and, following the work of JOLIBOIS in 1912 and of SCHLENK in 1929, the existence of an equilibrium: EQU 2RMgX.revreaction.MgR.sub.2 +MgX.sub.2
(R is a hydrocarbon radical, X is a halogen atom) is generally acknowledged.
According to SCHLENK (Berichte der Deutschen Chemischen Gesellschaft 64, 734 (1931)), the percentage of the form RMgX in the reaction product is generally low; for example, this percentage does not exceed 43% for any of the Grignard reagents including an ethyl, propyl, or phenyl radical and obtained in ether. This of course affects the reactivity of the Grignard reagent towards the numerous chemical substances with which it is able to react. In the following disclosure the percentage of the form RMgX in the product of the Grignard reaction will be referred to as the "purity" of the product.
A first object of the invention is to obtain organometallic halides in a pulverulent form directly utilizable for its subsequent applications. This result, which is achieved by a dry process, has permitted the discovery of organometallic halides of high purity--according to the preceding definition--frequently associated with the corresponding metallic hydride. These particular oganometallic halides are novel industrial chemical products. Another object of the invention is the application of these new products to the synthesis of perfectly anhydrous metallic halides.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
The accompanying drawing, which is incorporated in and constitutes a part of this specification, illustrates one embodiment of the invention and, together with the description, serve to explain the principles of the invention.